Creating graphs with nodes and edges in the editor (diagrams)


I’d like to know how to start with making editor extension with components that are used for example in Mecanim or in many additional Unity addons on the store.

Few questions:
Is there any component that would allow me easily create editable nodes (boxes with list of values)
Is there arrow component that can be easily make connections between these nodes, or do I need to extend basic components and do all the stuff that manages these things on my own by using editor primitives?
Is there any asset on the Asset Store that would help me with this? I saw quite few addons of this style that were looking quite similar regarding their components, unfortunately I was unable to find much information regarding this topic.

Any suggestions and leads are appreciated, thank you!

This forum thread has the best info and script code to get you started.